| 摘要 |
PURPOSE:To prevent boiling of water in the reference head tube to measure the water level accurately, by giving an heat insulating structure to the reference head tube and the pressure conducting tube. CONSTITUTION:External parts of pressure conducting tube 4 and reference head tube 7 and the external part of coupling tube 12 in the position corresponding to the inside of storage vessel 2 are coated with external tube 13 concentrically airtightly to have a dual-pipe construction, and external tube 13 has gas exhausted by vacuum pump 14 to form a vacuum heat insulating layer. Since condensed steam forms fixed reference water surface 9 in condensing tank 8, water level 11 is detected by measuring the differential pressure between reference water head 10 and nuclear reactor pressure vessel 1 by differential pressure converter 6. Even if the temperature in storage vessel 2 becomes high due to the accident of loss of the cooling material, water in reference head tube 7 is not boiled in the decompression process, and thus, water level 11 is measured accurately. |
